1. Field of the Invention
This invention relates to novel personal product compositions as well as to alkyl sulfooxyalkanoate surfactants used in the compositions and methods for the preparation of these surfactants. A portion of the surfactant molecule functions as a so-called "benefit reagent" which will form when the molecule is metabolized by enzymes present in the body or elsewhere or which will form when the molecule spontaneously hydrolyzes on the skin surface. Personal products compositions comprising these sulfooxyalkanoate compounds include hair/body shampoos, cleansing creams, conditioners, cosmetic applications, dental applications, underarm deodorant/antiperspirant applications and sunblock applications. Other applications include soaps, powders, lotions and therapeutic creams. This list is not intended to be exhaustive and other compositions in which surfactants may be used are also contemplated.
2. Prior Art
In the past decades, "mildness" has become an increasingly important criterion in selecting surfactants for personal products. The term "mildness" means that surfactants do not produce any skin irritation. Many consumers recognize the skin damaging effects surfactants may have. Therefore, a surfactant used for personal products should not only possess good surface active properties, but should also be safe on human skin.
Although many factors, e.g., removal of skin lipids, loss of naturally occurring hygroscopic materials in the stratum corneum, adsorption, protein denaturation, epidermal liposomal injury, are known to have an influence on skin irritation, it is generally believed that surfactants cause skin irritation by penetrating the stratum corneum and reacting with the inner cells of the epidermis. Accordingly, one approach to achieving "mildness" is to prevent surfactants from penetrating the stratum corneum and reacting with those cells.
A second approach for obtaining "mildness" is to design surfactants which can penetrate the stratum corneum but which, once they have penetrated, degrade to harmless components, possibly with the aid of enzymes. This second approach (the approach followed by the subject invention) attempts to take advantage of the enzymatic activity which is believed to be present in the sublayer of the stratum corneum. See Foster et al, Arch Derm. Res., 25:23-28 (1975) and Kermici et al, J. Soc. Cosmet Chem., 28:151-164 (1977).
It is also known in the art that hydroxy acids have beneficial effects on the skin. U.S. Pat. No. 4,197,316 to Yu et al. for example, discloses a non-irritating therapeutic composition for alleviating dry skin symptoms wherein the composition contains hydroxy acids (e.g., .alpha.-hydroxy butyric acid, lactic acid and citric acid). U.S. Pat. No. 4,294,852 to Widnaer et al. teaches skin treating compositions comprising hydroxy acids. U.S. Pat. No. 4,507,319 to Barret et al. also describes skin treatment compositions possessing .alpha.-hydroxy octanoate acid.
None of these patents teach a surfactant material which is able to deliver the hydroxy acid component to the skin.
Accordingly, it would be particularly beneficial to design compositions comprising a surfactant molecule wherein the surfactant not only breaks down inside the skin or which spontaneously hydrolyzes upon contact with the skin surface, but to design a molecule which, one it has been broken down in the skin or once it has hydrolyzed, will have a beneficial effect on (e.g., alleviating dryness, imparting antimicrobial activity, etc.) or will deliver a benefit to the skin.
In U.S. patent application No. 628,243, filed Dec. 17, 1990 and hereby incorporated by reference, the inventor of the subject application provides novel compositions comprising phosphate esters which are designed to break down or hydrolyze and to impart the beneficial reagent component described above. There is no description of compositions comprising the sulfooxy analogs of the present invention in that disclosure.
Peliska et al. in Biochemistry, 28: 1604-11 (1989), disclose simple sulfoenol pyruvate compounds prepared in order to study pyruvate kinase. The compounds are short-chained pyruvates which have no utility as surfactant materials. Further, there is no teaching at all that these compounds can be used as intermediates to prepare a beneficial reagent or of their use in compositions.
Certain commercially available sulfosuccinic alkyl esters are similar to the compounds of the invention. For example, Caryl, C. R., Industrial and Eng. Chem., 33 (6): 731 (1941) teaches compounds in which an alkyl ester of succinic acid is attached to a sulfonate group. These compounds are both structurally and chemically distinct from the sulfooxyalkanoate esters of the invention in that they comprise a sulfonate group rather than a sulfate group. The sulfate group is much more difficult to hydrolyze and will not accordingly readily provide a beneficial reagent such as is hypothesized is occurring with the compounds of the invention.
Stirton et al., Journal Amer. Oil Chem. Soc., 39: 490 (1962) teaches alkyl sulfoalkanoate compounds. Smith et al., Journal Amer Oil Chem. Soc., 44:405 (1967) teaches .alpha.-sulfo fatty acid ester compounds. Once again, both of these references teach sulfonate compounds rather than sulfate compounds. Sulfonate compounds are far less soluble and structurally unrelated to the sulfate compounds of the invention.
None of the compounds taught in the art are sulfate surfactant compounds which are readily able to hydrolyze and from a beneficial reagent in the skin.
Thus, it would be useful to provide compositions comprising novel molecules (other than the phosphate esters mentioned above) which contain a salt (i.e., at least a partial salt of one portion and an ester group in the other portion) such that (1) a hydroxy carboxylic acid ester; (2) a hydroxy carboxylic acid; (3) a sulfooxy carboxylate; and/or (4) an alcohol (e.g., fatty acid alcohol or glycerol) may form when the molecule in the composition is metabolized by enzymes in the skin or is hydrolyzed upon contact with the skin.
It is a further objective of the invention to provide compositions containing surfactants (having the beneficial reagent) which, as surfactants, are also relatively calcium insensitive, may foam well and are mild to the skin.